Continuous growth of proximal tubular kidney epithelial cells in hormone-supplemented serum-free medium.

An epithelial cell line from pig kidney (LLC-PK1) with properties of proximal tubular cells can be maintained indefinitely in hormone-supplemented serum-free medium. Continuous growth requires the presence of seven factors: transferrin, insulin, selenium, hydrocortisone, triiodothyronine, vasopressin, and cholesterol. The hormone-defined medium (a) supports growth of LLC-PK1 cells at a rate of approaching that observed in serum-supplemented medium; (b) allows vectorial transepithelial salt and fluid transport as measured by hemicyst formation; and (c) influences cell morphology. The vasopressin dependency for growth and morphology can be partially replaced by isobutylmethylxanthine or dibutyryl cyclic AMP. The medium has been used to isolate rabbit proximal tubular kidney epithelial cells free of fibroblasts

Retention of differentiated properties in an established dog kidney epithelial cell line (MDCK).

Madin-Darby canine kidney (MDCK) cells grown in tissue culture have the morphological properties of distal tubular epithelial cells, form tight junctions, and lack several proximal tubular enzyme markers. Adenylate cyclase in these cells was stimulated by vasopressin, oxytocin, prostaglandins E1 and E2, glucagon, and cholera toxin. Hormone-stimulated adenylate cyclase activity in isolated membrane preparations was dependent on low concentrations of GTP and had the MgCl2 and pH optima expected for the kidney enzyme. The results, as well as the demonstration of enhanced hemicyst formation induced by cyclic AMP, suggest that the MDCK cell line has retained the differentiated properties of the kidney epithelial cell of origin. When MDCK cells were injected into baby nude mice, continuous nodule growth was observed until adulthood was attained. Histological studies revealed the presence of two cell types: normal mouse fibroblasts which comprise 80--90% of the solid nodule mass, and MDCK cells, which formed epithelial sheets lining internal fluid-filled glands. Electron microscope analysis showed that the mucosal surfaces of the cells were characterized by microvilli which faced the lumen of the glands, that adjacent MDCK cells were joined by tight junctions, and that the serosal surfaces of the epithelial sheets were characterized by smooth plasma membranes which were lined by a continuous basement membrane. These observations lead to the conclusion that the MDCK cells retain regional differentiation of their plasma membranes and the ability to regenerate kidney tubule-like structures in vivo

unarXive: a large scholarly data set with publications’ full-text, annotated in-text citations, and links to metadata

In recent years, scholarly data sets have been used for various purposes, such as paper recommendation, citation recommendation, citation context analysis, and citation context-based document summarization. The evaluation of approaches to such tasks and their applicability in real-world scenarios heavily depend on the used data set. However, existing scholarly data sets are limited in several regards. Here, we propose a new data set based on all publications from all scientific disciplines available on arXiv.org. Apart from providing the papers' plain text, in-text citations were annotated via global identifiers. Furthermore, citing and cited publications were linked to the Microsoft Academic Graph, providing access to rich metadata. Our data set consists of over one million documents and 29.2 million citation contexts. The data set, which is made freely available for research purposes, not only can enhance the future evaluation of research paper-based and citation context-based approaches but also serve as a basis for new ways to analyze in-text citations. See https://github.com/IllDepence/unarXive for the source code which has been used for creating the data set. For citing our data set and for further information we can refer to our journal article Tarek Saier, Michael Färber: "unarXive: A Large Scholarly Data Set with Publications’ Full-Text, Annotated In-Text Citations, and Links to Metadata", Scientometrics, 2020, http://dx.doi.org/10.1007/s11192-020-03382-z

Protein uptake into E. coll during Bdellovibrio infection A process of reverse secretion?

AbstractBdellovibrio bacteriovorus is a small bacterial parasite that infects other Gram-negative bacteria, resides in the periplasm of the host cell, and utilizes host macromolecules as a source of nutrients. Evidence is summarized suggesting that B. bacteriovorus secretes proteases and nucleases synthesized in its own cytoplasm that are targeted to the cytoplasm of the host cell. Possible mechanisms for this trans-trimembrane protein transport process are discussed